Bleaching process



Patented Apr. 13, 1937 PATENT OFFICE 2,077,103 BLEACBING PROCESSEhrliart Franz, Leipzig, Germany No Drawing. Application February 9,1934, Se-

il'isal3 No. 710,527. In Germany December 28,

Claims.

5 the purpose of bleaching organic materials hydrogen peroxide and thosecombinations which are able to split up hydrogen peroxide in a waterysolution, for example persulphates, percarbonates, permono-sulfuricacids, perborates and perphosphates. As is well known, organic fiber,both natural and artificial, can be bleached in the bleaching-bath bymeans of such decolorants. Among the natural products it isparticularlythe animal, 1. e. nitrogenous materials, and the vegetablematerials, mostly free from nitrogen, that can be ameliorated by means01 such bleachingbaths. If the decolorants are used in a highlyeilicacious, i. e. active or actuated form, much oxygen is lost, becausethe decolorants sponzo taneously dissolve themselves in thebleachingbath and deliver their oxygen not only for the bleachingprocess. If, however, the bleaching solutions are stabilized or used ina stable form, the bleaching process, as is well known, is retarded verymuch and the bleaching eflect is a bad one.

For the present invention it is necessary that the material to bebleached is provided, at the spots which are to be bleached, withcombinations that are able to start and accelerate the bleachingprocess, either by depriving the originally stable bleaching solution ofits stabilizing substance or by reacting upon the effect of itsstabilizing substance. According to the present invention this reactiontakes place in the very proximity of the spots to be bleached. Adeterioration of the bleaching solutions by soiling the perhapsllxiviated actuating substance can be avoided by using thebleaching-baths only for the impregnation of the material in question,or by squirting or brushing the decolorant on the material to bebleached and finishing the bleaching process by leaving the material ina moist state, where it is suitable to work at a raised temperature. Ofcourse it is possible to apply actuating substances that do not tend topass into the stabilized bleaching-bath. As the decolorant is worn outonly at the spots that are really bleached, the decolorant is used upvery economically. As stabilizing substances for the bleaching-baths,respectively for the decolorants, those which are known hitherto arenearly all taken into account, especially, however, colloid substances,such as glue, colloid silicic acid, solutions of glucosides, tin-salts,organic combinations such as mannite, phenols, particularly thoseinorganic or organic combinations which give the solution a low value ofpH. As actuating substances we practicably use the well known metallicsalts, efflcacious as catalyzers, or enzymes and ferments, for exampleextracts of yeast, as well as oxidases and peroxidases and finally thosecombinations which give solutions of a high value of pH. If a decolorantsolution stabilized by an acid is used, it is very practicable to chargethe --material with those substances which are able to increase thevalue of pH, for example with alkalies, alkalic carbonates, salts suchas soda having an alkaline reaction, etc. If the latter are applied, itis possible to use the actuating material during the preparatorytreatment of the material to be bleached and to leave it partly in thesame. Enzymes are found in most of the raw materials, so that it ispossible to keep part of the enzymes or all of them in the material tobe bleached, by means of a suitable choice of the preparatory treatment.

The result of the aforesaid process is a very quick bleaching andtherefore a' considerable sparing of the material. It has proved'mpracticable to apply decolorants that are stabilized by the adjustmentto a low value of pH, as in the bleaching process with such meanssimultaneous reactions easily appear, which deteriorate the originallygood bleaching, the material turning yellow. Oxalic acid provedparticularly practicable, because-in this case the material cannot turnyellow. By means of oxalic acid even sensitive materials, such as wool,may be bleached inan absolutely satisfying way. Also in this case ashort treatment, lasting only a few minutes, of the material with thebath itself is sufllcient; the bleaching process may then be finished byleaving the material in a moist and eventually warm state. This processproved particularly suitable in the bleaching of woolen slivers. Insteadof oxalic acid there may also be used phosphoric acid or boric acid withgood success. Lactic acid and formic acid may also be applied. In orderto spare the material it is practicable to add, after the bath, othersubstances that spare the fibres, for example formaldehyde, glue, sugar,It is especially worth remarking that the oxygen of the baths can beused up to an evanescent remainder, if very efflcacious actuatingsubstances are applied. Therefore it is possible to apply baths of avery low percentage and to finish the bleaching process in strongerbaths. The preparatory or final bleaching of the material can also takeplace. according to any other method. It is worth remarking, too, thatthe stabilized bleaching-baths may be warmer than the usualbleaching-baths applied in other cases, the result of it being a bettersoaking of the decolorant.

To the extent to which this invention also touches upon an acid bleach,as well as a continuous bleaching process, attention is called to mycopending applications entitled: Process for bleaching, Serial No.712,608, filed February 23, 1934, and Continuous bleaching process,Serial No. 712,609, filed February 23, 1934, respectively.

The following examples shall explain theprocess according to the presentinvention, but the invention shall not be limited to these examples.

Example 1 Cotton is, as usual, washed in an alkaline bath 7 in thepresence of 0.3 per cent. of hydrosulphite of sodium formaldehyde. Aftera short rinsing the material, which still reacts in alkaline fashion, isput into a bleaching-bath of 5 parts by weight of hydrogen peroxide alitre, stabilized by an addition of 0.03 per cent. of phosphoric acid.It is suitable to bleach the material between 20 and 60 and to leave itin the bath for about 5 minutes. Then the material is squeezed off andkept at a temperature of until the bleaching process is finished.

Instead of phosphoric acid there may also be used sulphuric acid. Inthis case it is suitable to add to the bleaching-bath somesodium-sulphate (about 0.2 per cent). Oxalic acid, too, may be used asstabilizing substance, as well as isobutylnaphthalene-sulpho-acid orboric acid. If instead of hydrogen peroxide perborate of sodium is usedfor the bleaching-bath. the quantity of the acid must be a littlelarger. The bleaching process, however, lasts only inconsiderablylonger.

Example 2 100 parts by weight of jute are preparatorily bleached with800 parts by volume of bleaching solution obtained from 1 part by weightof chloride of lime by converting with sodasolution (containing 0.6 partby weight of calcined soda) for 12-16 hours at the temperature of theroom. Then the material is rinsed, as usual, some thicsulphate beingadded in the beginning, and edulcorated, if necessary, with a 5 percent. oxalic acid solution. A distinct alkalic reaction of the materialupon litmus-paper can still be observed. The bleaching process is nowfinished in a bleaching-bath containing 0.5-1 per cent. of hydrogenperoxide, stabilized by l per cent. of sulphuric acid, an insignificantquantity of aluminium sulphate being added, if necessary. The materialremains in the bath for about 10 minutes at the temperature of the roomand is then kept in a moist state for 3-4 hours at a slightly raisedtemperature.

Instead of sulphuric acid there can be used phosphoric acid,isobutyl-naphthalene-sulphoacid, oleyl-methyl-amino-ethane-sulpho-acidand acids of that kind or the salts thereof. Instead salt.

itable.

of aluminium salt-there can be used a magnesium In order to obtain aparticularly clear, white colour, a third bleaching-bath can be applied.For this purpose a bath of 0.1 per cent. of hyposulphite of sodium, 0.1per cent. of calcined soda and 0.1 per cent. of oleine soap proved prof-The bleaching process lasts about 20 minutes at a temperature of aboutExample 3 Jute is freed from dust and then put, for several hours, intoa bath containing 0.5 per cent. of purchasable hydrogen peroxide. Theenzymes which are in the raw jute eifect that the usually ratherinactive decolorant solution produces a yellowish white material. Nowthe material is impregnated in a bath of 2-3 per cent. of hydrogenperoxide stabilized by an addition of oxalate of sodium, and kept at anormal or slightly raised temperature, until it is as White as possible.The first bath must not be stabilized, as solutions of such a lowpercentage are already stable. The second bath can also be stabilized byother combinations of a low value of pH or by colloids, such as silicicacid gelatine or by phenols, amines, etc.

Example 4 parts by weight of animal hair, for example hair of theAngora-goat or sheeps wool, are, as, usual, washed with soap and sodaand well rinsed. The animal hair retains about 1 per cent; of soap.After having been made into sliver the material is put, for two minutes,into a bath of 0.5 per cent. of hydrogen peroxide and 0.03. per cent. ofoxalic acid at a temperature of 40, some oxalate being added ifnecessary. Then the material is flied or squeezed off and dried for alonger time at a lower temperature, or for a shorter time at a highertemperature, for example by making the material pass over warmcylinders. It is worth remarking that the animal material is injuredonly quite insignificantly, and'particularly that the loss of weight isquite unimportant.

Example 5 100 parts by weight of bat stumps corroded, as usual, bymercury salts, are put into 600 parts of a bleaching-bath of 3 per cent.of hydrogen peroxide and 1 per cent. of bitter salt (epsomite) and thenkept in a moist state. The bleachingbath is stabilized by 0.1-0.2 percent. of lactic acid or phosphoric acid or by 0.1 per cent. of mannite.The bleaching process lasts about 3 hours at a temperature of 40-50",about 24 hours at the normal temperature in the room.

Example 6 100 parts by weight of wool in the form of a cord are put, for30 minutes at the normal temperature in the room, into 600 parts of abath of 0.1 per cent. of permanganate of potassium very weaklyacidulated by sulphuric acid or to which about 1 per cent. of bittersalt was added. Now the wool is dyed brown by hydrate of dioxide ofmanganese. Then the material is carefully rinsed and put into a bathcontaining 0.2-0.5 per cent. of hydrogen peroxide and 0.2 per cent. ofsulphuric acid and 0.5-1 per cent. of oxalate of sodium, for about 2minutes at a temperature of 30-40". Hereafter the material is put into asimilar bath containing 2 per cent. of hydrogen peroxide and thecorresponding quantity of stabilizing substance. After about 10-30minutes the material is taken out of the bath, carefully rinsed andcleared in a bisulphite bath of about 1 per cent. of bisulphite ofsodium and 0.6 per cent. of sulphuric acid. In order material iscarefully rinsed and freed from acid in the usual way.

' A particular softness of the material is produced by an addition ofprotective colloids, for example a small quantity of glue or a smallquantity of tanning substance given to the bleachingbath. The damagedone to the material which is to be bleached is considerably reduced bya preparatory treatment of the material with aldehydes, for exampleformaldehydes, acetaldehydes, chloraldehydes, etc., or by an addition ofthe aforesaid combinations to the bath.

The present bleaching process is not limited to the bleaching offibrils. By means of this process there can as well be bleached otherorganic materials,'such as horn, bone, resin, artificial resin, legumes,Indian corn, flour, etc. Of course the decolorant can also be applied byinjection or in a similar fashion. a I It is possible to bring thebleaching means on the material by impregnating. For this process astabilized bleaching bath is taken; the material is impregnated bythat,.whereby it is useful to provide said material with compoundsactuating the bleaching process. Or the material is impregnated by ableaching bath stabilized as usual and than said material is given in awatery solution which contains a compound actuating the bleach. Inreferring herein to stabilized hydrogen peroxide bleaching solutions Ipresume such solution to be substantially non-alkaline, i. e., that itdoes not give an alkaline reaction with litmus, because otherwise thesolution cannot be stable.

Having thus described my invention what I claim and desire to secure byLetters Patent is:

1. The process which comprises the steps of applying to organic fiber tobe bleached accelera-. tors free of heavy metal, and of causing aqueoussolutions of up to 3% hydrogen peroxide rendered stable by the additionof stabilizers free from heavy metal to act on said organic material,the accelerators locally activating the bleaching.

2. The process which comprises the steps of applying to organic fiber tobe bleached accelerators free of heavy metal, and of causing aqueoussolutions of up to 3% bleaching agents giving oil hydrogen peroxide andrendered stable by the addition of stabilizers free from heavy metal toact on said fiber, the accelerators activatin the bleaching solutionapplied to said fiber.

3. The process which consists in causing aqueous solutions of up to 3%hydrogen peroxide rendered stable by the addition of stabilizers freefrom heavy metal to act on organic fiber carrying enzymes as activatorsfor accelerating bleaching.

4. In combination with a hydrogen peroxide bleaching solution forfibrous material, the sepa- ,rate application of a stabilizer for saidsolution and of an accelerator, the accelerator being applied to saidmaterial before it is bleached by the stabilized solution.

5. The process of claim 1, carried on first in a. used and thencontinued in a fresh bleaching solution.

EERHART FRANZ.

